Noisy signal based background technique for gain error correction in pipeline ADCs

The paper presents a new digital technique for background calibration of gain errors in pipeline ADCs. The proposed algorithm estimates and corrects both the MDAC gain error of the stage under calibration (SUC) and the global gain error associated with the least significant stages. This process is performed without interruption of the conversion and without reduction of the dynamic range. It uses a stage with two input-output characteristics depending on the value of a digital pseudorandom noisy signal to modulate the output residue of the SUC and to estimate the calibration code by an adaptive averaging process. The proposed method introduces no significant modifications in the analogue blocks of the pipeline ADCs, making this technique a very promising alternative for background calibration of the nonlinearity associated with the gain errors. Simulation results have proved the stability of the algorithm and the tracking capability for fast gain error changes considering second order effects in both the sub-ADC of the SUC and the back-end stages.